Sendmail: messages being blocked by atmailcloud.com

Robert S · 03-12-2024, 08:58 PM

I have been unable to send messages to certain ISPs, and am getting these messages:

Quote:

2024-03-09T17:44:16.863099+11:00 debian sm-mta[27973]: 42740Zgm790989: to=<XXXXX@iinet.net.au>, ctladdr=<MYUSER@MYDOMAIN.net.au> (1004/1004), delay=2+02:43:41, xdelay=00:00:00, mailer=esmtp, pri=27852616, relay=mx-20.au-east.atmailcloud.com., dsn=4.5.0, stat=Deferred

The common factor is that they all use mx-20.au-east.atmailcloud.com. Eventually I'm notified that the messages have not been delivered.
If I connect to mx-20.au-east.atmailcloud.com

Quote:

$ telnet mx-20.au-east.atmailcloud.com 25
Trying 3.106.43.229...
Connected to mx-20.au-east.atmailcloud.com.
Escape character is '^]'.
451-conn-401: IP [XXX.XXX.XX.XX] is listed on Cloudmark CSI Suspect - is
451 currently being throttled

We are a small business, and don't send bulk email. There's no evidence that we harbour a robot that is sending out spam messages.
I have tried to de-list my IP address from Cloudmark, but their web page says I'm not listed.

Is there any way I can resolve this using my Sendmail config - I assume if the connection is throttled, it might still be possible to make a connection.
My sendmail config:

Quote:

divert(-1)dnl
divert(0)dnl
define(`_USE_ETC_MAIL_')dnl
include(`/usr/share/sendmail/cf/m4/cf.m4')dnl
VERSIONID(`$Id: sendmail.mc, v 8.12.3-6.6 2003-09-17 18:35:09 cowboy Exp $')
OSTYPE(`debian')dnl
DOMAIN(`debian-mta')dnl
undefine(`confHOST_STATUS_DIRECTORY')dnl #DAEMON_HOSTSTATS=
MASQUERADE_AS(`MYDOMAIN.net.au')dnl
FEATURE(`masquerade_envelope')dnl
FEATURE(`allmasquerade')dnl
LOCAL_DOMAIN(`MYDOMAIN.net.au')dnl
define(`confDOMAIN_NAME', `MYDOMAIN.net.au')dnl
FEATURE(`use_cw_file')dnl
FEATURE(`smrsh')dnl
define(`confLOG_LEVEL',10)dnl
FEATURE(`access_db')dnl
FEATURE(`blacklist_recipients')dnl
FEATURE(accept_unresolvable_domains)dnl
FEATURE(`dnsbl', `xbl.spamhaus.org',`"550 Message from "$&{client_addr}" rejected as spam - see http://www.spamhaus.org/query/bl?ip="$&{client_addr}"')dnl
INPUT_MAIL_FILTER(`opendkim', `S=inet:8891@localhost')
INPUT_MAIL_FILTER(`greylist',`S=local:/var/run/milter-greylist/milter-greylist.sock,F=, T=S:4m;R:4m')
define(`confMILTER_MACROS_CONNECT', `j, {if_addr}')
define(`confMILTER_MACROS_HELO', `{verify}, {cert_subject}')
define(`confMILTER_MACROS_ENVRCPT', `{greylist}, {client_resolve}')
INPUT_MAIL_FILTER(`clmilter',`S=local:/run/clamav/clamav-milter.ctl,F=, T=S:4m;R:4m')dnl
define(`confMILTER_MACROS_ENVFROM', ``i, {auth_type}, {auth_authen}, {auth_ssf}, {auth_author}, {mail_mailer}, {mail_host}, {mail_addr}'')
define(`confMAX_MESSAGE_SIZE', 20000000)dnl
define(`confBAD_RCPT_THROTTLE',`3')dnl
define(`confMAXRCPTSPERMESSAGE', `200')dnl
define(`LOCAL_MAILER_PATH', `/usr/bin/procmail')dnl
FEATURE(`local_procmail')dnl
include(`/etc/mail/sasl/sasl.m4')dnl
define(`confAUTH_OPTIONS', `p,y')dnl
include(`/etc/mail/tls/starttls.m4')dnl
LOCAL_CONFIG
O CipherList=HIGH
O ServerSSLOptions=+SSL_OP_NO_SSLv2 +SSL_OP_NO_SSLv3 +SSL_OP_CIPHER_SERVER_PREFERENCE
O ClientSSLOptions=+SSL_OP_NO_SSLv2 +SSL_OP_NO_SSLv3
MAILER(`procmail')dnl
MAILER(local)dnl
MAILER(smtp)dnl

RandomTroll · 03-12-2024, 11:40 PM

I just tried

Code:

telnet mx-20.au-east.atmailcloud.com 25

got:

Quote:

550-conn-502: IP [xxx.yyy.zzz.www] is listed on Abusix RBL - please refer to
550 https://lookup.abusix.com/search?q=xxx.yyy.zzz.www
Connection closed by foreign host.

Can anyone?

You can relay your mail through another server, if you have permission. I relay mine through my alma mater's alumni server. Otherwise, I think not.

descendant_command · 03-13-2024, 12:22 AM

Quote:

Originally Posted by Robert S

Is there any way I can resolve this using my Sendmail config

No.

Robert S · 03-13-2024, 04:14 AM

I've managed to use my ISP's smarthost (found on a forum). I'm not sure how long that will be supported. It took me a long time to work out the correct SPF record. Otherwise I can use another server that I run. I'm hoping that eventually the problem with atmailcloud will eventually go away . . .

TenTenths · 03-13-2024, 04:36 AM

Quote:

Originally Posted by RandomTroll

I just tried

Code:

telnet mx-20.au-east.atmailcloud.com 25

Can anyone?

Yes, no problem.

Code:

220 mx.i-0f92385efafd7ab5a - SMTP Ready

Of course I was trying from a server that I know isn't on any RBL blacklist and isn't from a residential IP address, it also has fully functional forward and reverse lookups.

The OP has my sympathies as I've had several times where it's been difficult to get an IP off an RBL.